Various gauge means for checking the accuracy of a keyway cut in a shaft are known in the art. The devices as known in the art, however, are not capable of measuring the centrality of Woodruff keyway walls to the centerline of the keyway. A key is a means inserted into a given space to lock or hold parts of a mechanism or structure together, for example a small piece of metal fitting into a matching slot in a hub of a wheel or the like and the shaft on which the wheel is mounted so that torque is transmitted from one to the other. A Woodruff key is a key having the form of a nearly semicircular disk fitting into a recess in a shaft, as shown in FIG. 2. Accordingly, a Woodruff keyway is curved as shown in FIG. 1. A Woodruff keyway is formed in a shaft so that the curve extends along the length of the shaft and not widthwise or crosswise in the shaft. No measuring devices are currently known capable of measuring the centering of Woodruff keyways. In order to check for the centering of Woodruff keyway side walls, separate time consuming measurements are required unless an instrument having a key cut to size to fit within the keyway is utilized. Such an instrument results in added cost to the cutting and measuring operation since the device is suitable for use with only one size keyway.
For example, the use of a horizontal indicator dial and probe in conjunction with a micrometer is currently available on the market through the company A.u.W. Busch GmbH and Company. This device, however, does not contain any means for measuring the perpendicularity of a keyway side wall to the centerline of the keyway. It cannot in particular check a Woodruff keyway centerline.
U.S. Pat. No. 4,970,799, which has the same assignee as the present invention, discloses a device for measuring the perpendicularity of a shaft keyway's side walls to the centerline of the keyway cut in a shaft, as well as measuring the centering and parallelism of the keyway formed and a method of using the device. In using the device disclosed in the '799 patent to measure a keyway, however, the device is positioned in relation to the angle formed at the juncture of the base wall with the side wall When the keyway to be measured is in the form of a Woodruff keyway, this juncture is curved, thereby making it impossible to obtain a consistent stable measurement.
More particularly, the preferred embodiment of the device disclosed in the '799 patent, as shown in FIG. 12 herein, includes a micrometer 33 slidingly attached to the device, a vertical indicator dial 47 slidingly attached to the device and connected to a vertically extending probe 55 which is positionable in a shaft keyway 71, a horizontal indicator dial 59 slidingly attached to the device and connected to a horizontally extending probe 69 positionable in a shaft keyway 71, and two stationary legs extending downward from the device for seating in a shaft keyway, only one stationary leg 75 being shown in FIG. 12.
In operation, the horizontal indicator dial and horizontal probe are utilized to check the centering and parallelism of the keyway and the vertical indicator dial and vertical probe are utilized to check the perpendicularity of the keyway side walls to the centerline of the keyway.
In use, the two stationary legs are positioned in one of the base angles which are formed at the point which one side wall of the keyway meets the base wall of the keyway. The micrometer is then positioned so that it abuts the approximate centerline of the shaft. To check the centering of the keyway, the tip 77 of the horizontal probe 69 is positioned approximately one-half the distance across the keyway from the two stationary legs of the device. The micrometer is set at zero while making sure that the horizontal probe tip remains in contact with the keyway base. The horizontal indicator dial is then set to zero. Thereafter, the device is removed from the shaft keyway and turned 180.degree. and repositioned in the keyway in the same manner but without adjustment to the dials or probe position. The reading on the horizontal indicator dial should still be zero. If it is not, the micrometer is moved in or out to provide the variation present which indicates the correction to be made.
To check the parallelism to the centering of the keyway, the same procedure is followed as in checking the centering of the keyway with the exception that rather than turning the gauge 180.degree. at the same point in the keyway, the device is moved to the opposite end of the keyway. The reading on the horizontal indicator dial should remain at zero following the repositioning, and if not, the micrometer is turned until the horizontal indicator dial registers zero. The reading on the micrometer then indicates the variation and the correction to be made.
To check the perpendicularity of the keyway side walls to the centerline of the keyway, the vertical indicator dial and probe are utilized. The device is positioned in the keyway in the same manner with respect to the stationary legs and micrometer as for checking the centering and parallelism of the shaft. The vertical indicator probe is adjusted downward until the probe tip touches the keyway side wall a suitable distance below the top edge of the side wall, for example, approximately 0.1 inch down the side of the wall. The vertical indicator dial and micrometer are each set to zero. The device is then removed from the keyway and turned 180.degree. and repositioned in the shaft keyway making sure the stationary legs are seated properly in the keyway base and that the vertical probe tip is touching the opposite side wall the same distance down the side wall of the keyway as when positioned against the first side wall. The reading on the vertical indicator dial should still be zero, and if not, the reading on the indicator dial will tell the variation, and accordingly, the correction to be made.
The measuring apparatus as disclosed in U.S. Pat. No. 4,970,799, however, is not suitable for consistently and accurately measuring Woodruff keyways due to the manner of placement of the stationary legs in relation to the base wall and side walls of the keyway. The measuring of a Woodruff keyway, due to its curved walls would result in inconsistencies in readings.
Accordingly, the art does not describe a device which is economical and capable of accurately and consistently measuring the centrality of a Woodruff keyway side walls to the centerline of a shaft keyway either alone or in combination with another means of measuring a keyway shaft.